Walgreen Co. wants more customers to fill 90-day prescriptions in its stores, a move it says will make it easier for patients to stick to their drug regimens and save millions of dollars in healthcare costs.

The move would also help Walgreen’s bottom line, as 90-day prescriptions are more profitable to fill than monthly ones.

Many insured Americans receive prescriptions for chronic conditions through the mail, since filling prescriptions via the mail cuts down on costs for insurers.

Now Walgreen — the largest U.S. drugstore chain with 7,655 stores — is showing off new data suggesting that companies can save money if people fill such prescriptions at stores, getting three months’ worth of drugs at a time.

Walgreen saved Navitus Health Solutions, a Wisconsin-based pharmacy benefit manager, $3.3 million in seven months with a plan that offered 90-day prescriptions at its stores, Walgreen Chief Innovation Officer Colin Watts said in an interview.

“It’s much cheaper for a plan to keep somebody adherent with their medications then to pay for the hospitalizations and other issues that can pop up when somebody is not adherent,” Watts said.

Walgreen has seen up to a 15 percent improvement in compliance to medication when someone moves from a 30-day prescription to a 90-day one, he said.

The majority of prescriptions Walgreen fills are maintenance prescriptions for conditions such as diabetes or high blood pressure, so moving more customers to 90-day refills could have a big impact on its pharmacy profits. Plus, people coming into the store to pick up a prescription could also buy other items, boosting sales growth.

“We think this is going to be one of the fastest growing parts of the Walgreen’s pharmacy business for several years to come,” Watts said.

Aging baby boomers, in particular, are expected to drive the growth of maintenance medications.

The plan, which will be discussed Wednesday at Walgreen’s annual meeting, is not an entirely new push for the company. Walgreen launched a 90-day refill program in late 2009 and signed up Caterpillar Inc as the first client in a direct-to-employer drug pricing program.

Walgreen continues to feel the heat from CVS Caremark Corp , which has given pharmacy benefits customers the option of picking up drugs in its stores at their mail-order price under its popular Maintenance Choice program.

Walgreen’s historical growth of 90-day prescriptions has basically been in line with market growth, Watts said. Now the Deerfield-based company is making a concerted effort to grow its piece of the business.

After discussing the “Go 90” program with employers and other payers for a year, it is taking its pitch to the public. ”Get three refills in one, and for three months you’re done,” the company says in advertising that will debut in the coming weeks.